I have used RC, QuietRock, SoundBoard. QuietRock is effective but very expensive and she's HEAVY! Lastly, RC channels can be short now and then.
Regards,
Taylor
P.S. If you have some extra time and don't mind wasting a couple inches for any rooms. You can put a 2x6 bottom plate and top plate with interchange 2x4 studs for any dividing wall and add two layers of 5/8" sheetrock, insulation on each side of the wall. This is the cheapest and effective way of not buying QuietRock. As for me I don't have this option, condo needs as much room as possible, especially here in California. The clients do not want to hear that they are losing a couple of each per room and etc... Not a good selling point.